Fuel injection valve for internal combustion engines

ABSTRACT

Fuel injection valve with a nozzle body having a central guide hole and, to the side of the guide hole, a supply channel curved in an approximately circular manner with a radius, both of which open into a pressure chamber, the supply channel being formed by an erosion device, and in another configuration the nozzle body having a step at its face end. The construction features give the nozzle body great pressure resistance.

The invention concerns a fuel injection valve and a production process.

This kind of fuel injection valve is known from the document EP 0 363142 A1. In the nozzle body of the known fuel injection valve, the wallbetween the guide hole and the fuel supply channel is under an extremelyhigh injection pressure. The fuel supply channel runs, starting from theface of the nozzle body, first essentially parallel to the guide holebefore curving off in the direction of the pressure chamber and finallyopening into the pressure chamber.

The task of the invention is to increase the pressure resistance of thefuel injection valve.

Further advantageous configurations and improvements offered by theinvention are given in the sub-claims.

One advantage of the invention consists of increasing the pressureresistance of the nozzle body. Another advantage lies in the low cost ofproduction.

A fuel injection valve, especially for diesel fuel, has to have highpressure resistance in order to withstand the high fuel pressure. Thepressure resistance depends on the minimal wall thicknesses that can beachieved in the components of the fuel injection valve. The formation ofa curved supply channel in the nozzle allows wall thickness to beincreased in critical areas and hence provides high pressure resistance.

The invention is illustrated in more detail below in the figures:

FIG. 1 shows a longitudinal section through part of a fuel injectionvalve,

FIG. 2 shows a longitudinal section of a first example of embodiment ofa nozzle body,

FIG. 3 shows a longitudinal section of a second example of a nozzle bodyand an intermediate piece, and

FIG. 4 shows a basic diagram of the method for producing a curved supplychannel in a nozzle body.

Elements of the same construction or function generally have the samereference numbers in FIGS. 1 through 4.

The part of a fuel injection valve shown in FIG. 1 has nozzle body 300with a rotationally symmetrical basic shape that is attached to nozzleholder body 100 by means of sleeve-shaped coupling ring 600 withintermediate piece 200 between them.

Nozzle body 300 is subdivided, from its face end in the direction ofnozzle holder body 100, into the following sections: guide area 310,pressure chamber area 330, shaft area 350 and nozzle tip 370 thatterminates nozzle body 300. The face end is configured as an annulararea with its normal line being parallel to longitudinal axis 301 of thenozzle body.

Nozzle body 300 has a central nozzle body hole starting at its face endand ending at its nozzle tip 370, with a diameter and function thatvaries with the body sections of nozzle body 300. In the nozzle bodyhole there is nozzle needle 500 which is subdivided in the direction ofnozzle tip 370 into guide plunger 510, ring collar 520, shaft plunger530 and valve tip 540.

Guide area 310 has central guide hole 312 which serves to guide guideplunger 510 and which has hole opening 314 on the face of guide area310.

Connected to guide area 310 is pressure chamber area 330 which haspressure chamber 334. Guide hole 312 opens into pressure chamber 334into which guide plunger 510 is guided. Preferably, in pressure chamber334, guide plunger 510 passes into conically tapered ring collar 520which fits into shaft plunger 530.

To the side of guide hole 312 there is supply channel 338 whichpreferably opens into pressure chamber 334. Supply channel 338 hassupply opening 342 on the face end of guide area 310 and is curved overits entire length. The curve is preferably formed in an approximatecircle. The centerline of supply channel 338 forms a plane preferablyrunning through longitudinal axis 301 of nozzle body 300.

Shaft area 350 connects to pressure chamber area 330 and has shaft hole355 which connects to pressure chamber 334 and through which shaftplunger 530 runs.

Pressure chamber 334 is designed as a preferably symmetrical recess thatis loopshaped in cross-section and which lies between guide hole 312 andshaft hole 355. In the area of the upper part of the loop, the wall ofguide hole 312 makes an angle preferably in the 90° range with the wallof pressure chamber 334. In the area of the lower part of the loop,pressure chamber 334 converges conically and the wall of pressurechamber 334 passes at a flat angle into the wall of shaft area 350.

Conical nozzle tip 370 which has inside valve seat 374 for acceptingvalve tip 540 connects to shaft area 350. Nozzle tip 370 has at leastone injection hole 378 through which the fuel is injected into thecombustion chamber of the combustion engine. The axial movement of valvetip 540 controls the supply of fuel into the combustion chamber, withvalve tip 540 closing off injection holes 378 and interrupting the flowof fuel to injection holes 378 in the neutral state. The fuel is guidedin nozzle body 300 from supply channel 338 via pressure chamber 334,shaft hole 355 and valve seat 374 to injection holes 378.

The outside of nozzle body 300 is preferably stepped at the pressurechamber 334 level and at the shaft area 350 level, with the diameter ofnozzle body 300 being reduced in the direction of valve tip 370.

Intermediate piece 200 is a hollow cylinder and has central plunger hole215 to guide plunger 400 and supply channel 235 located to the side,preferably approximately parallel to plunger hole 215.

Intermediate piece 200 limits the lift of nozzle needle 500 sinceplunger hole 215 has a smaller diameter than guide plunger 510 of nozzleneedle 500.

Plunger 400 transfers the axial movement produced by a control valve oran actuator to nozzle needle 500. Nozzle needle 500 exerts on plunger400 a axial force in the direction of plunger 400 that is produced bythe fuel pressure on ring collar 520 and on the active annular face atvalve tip 540.

For illustration, some reference numbers from FIG. 1 are also listed inFIG. 2.

FIG. 2 shows details of the fuel injection valve from FIG. 1 with nozzlebody 300, the supply channel 338 of which is preferably formedapproximately in the shape of a circle by means of the erosion processdescribed in FIG. 4. The curve of supply channel 338 at its centerlinehas a first radius r1.

The area lying between the shoulder at the level of pressure chamber 334and the face end of guide area 310 is the flange area with flange lengthdl and flange diameter db at the pressure chamber 334 level.

Between supply channel 338 and guide hole 312 there is wall 346. At theopenings of supply channel 338 and guide hole 312 into pressure chamber334, wall 346 has the minimal thickness d. A large wall thickness dleads advantageously to a high pressure resistance of nozzle body 300.Supply channel 338 makes angle a with guide hole 312. Wall thickness d,depends, among other things, on angle a, first radius r1, flangediameter db and flange length dl.

The smaller the flange length dl at a given position of the shoulder atthe pressure chamber 334 level and the greater the flange diameter db,the smaller the first radius r1 can be, which leads to a greater angle aand advantageously to a greater wall thickness d.

A preferred embodiment of the nozzle body from FIG. 2 has a flangediameter db of 14.3 mm and a flange length dl of approx. 15 mm. In thisembodiment, the first radius r1 is between 30 and 50 mm, preferablyapprox. 35 mm. Angle a is roughly in the 30° to 40° range, preferablyapproximately 33°.

Other embodiments with different flange diameters db and flange lengthsdl accordingly have different first radius r1 and angle a ranges.Preferably angle a is in the 30° to 40° range and initial radius is inthe 30 to 50 mm range.

FIG. 3 shows another example of embodiment of nozzle body 300 withintermediate piece 200.

Unlike the example of embodiment from FIG. 2, guide area 310 is steppedby a step cut into upper body section 316 with annular face 322 and intolower body section 318 with annular shoulder area 324, with upper bodysection 316 placed at the face end of guide area 310. The normal linesof face area 322 and shoulder area 324 are preferably approximatelyparallel to longitudinal axis 301 of nozzle body 300. Upper body section316 has a smaller diameter than lower body section 318. Face area 322has hole opening 314 and shoulder area has supply opening 342.

The axial difference in height between face area 322 and shoulder area324 is step length 1 a.

The curve of supply channel 338 has at its centerline a second radius r2which, with a given nozzle body 300 geometry, is smaller than the firstradius r1 from FIG. 2. The length of supply channel 338 is shortened bythe step, and this advantageously allows a faster and morecost-effective production to be achieved, e.g., with a productionprocess described by means of FIG. 4.

The connection indicated in FIG. 2 between wall thickness d, angle a,first radius r1, flange diameter db and flange length dl appliescorrespondingly in the example of embodiment in FIG. 3, where the curveof supply channel 338 is here represented by second radius r2. There isalso a connection with step length 1 a: the larger step length 1 a, thesmaller second radius r2 can be, which leads to a greater angle a andadvantageously to a greater wall thickness d.

This connection also applies to nozzle bodies configured differentlyfrom the shapes given in the examples.

One embodiment of the nozzle body from FIG. 3 has a flange diameter of14.3 mm and a flange length of approx. 15 mm. Depending on step length 1a, second radius r2 is in the 5 to 10 mm range, preferably approx. 7 mm.Angle a is in the 40° to 70° range, preferably approx. 60° . Thepreferred form occurs at a step length of approx. 9 mm.

Other forms with differing flange diameters db and flange lengths dlhave corresponding first radius r1 and angle a ranges. Preferably secondradius r2 is in the 5 to 10 mm range and angle a is in the 40° to 70°range.

Intermediate piece 200 is divided in an axial direction into hollowcylindrical supply area 220 and hollow cylindrical plunger area 240 by astep cut on its inside facing plunger hole 215, with plunger area 240having a smaller inside diameter than supply area 220. Plunger area 240is located closer than supply area 220 to nozzle holder 100.

Supply channel 235 runs in the casing 212 of supply area 220 and plungerarea 240 preferably approximately parallel to plunger hole 215.

The step in intermediate piece 200 ends at the guide area 310 steplocated at the face end of nozzle body 300. Supply channel 338 of nozzlebody 300 connects to supply channel 235 of intermediate piece 200.

Locating face 324 of nozzle unit 300 lies level to the face area ofintermediate piece 200. A connection that is resistant to high pressuredevelops due to the force of pressure between nozzle body 300 andintermediate piece 200.

FIG. 4 shows erosion device 700 with which approximately circular supplychannel 338 is led into nozzle body 300. Erosion device 700 has erosionelectrode 701 which is circular in shape to conform to the desired firstor second radius r1, r2 of the curve in supply channel 338. Erosionelectrode 701 is clamped in electrode holder 702 which is moved alongthe arc of a circle, with its centerpoint being the same as thecenterpoint of the desired curve of supply channel 338. The diameter oferosion electrode 701 is only slightly smaller than the desired diameterof supply channel 338. Erosion electrode 701 is clamped into electodeholder 702 with a protrusion, the protrusion being somewhat greater thanthe length of supply channel 338.

With this process, it is advantageously possible to produce supplychannel 338 exactly and in one work step.

Alternatively, it is possible to push curved erosion electrode 701through a fixed, also curved electrode guide, which reduces the tendencyof erosion electrode 701 to fluctuate, which advantageously leads tocloser production tolerances. Erosion electrode 701 is guided to aminimal distance from nozzle body 300 during the performance of theerosion process. The metallic material of nozzle body 300 is removed bymeans of electrical discharge. This is a thermal removal process inwhich a succession of electrical discharges is used to remove metalmaterial from nozzle body 300.

To produce the electrical discharges, a high voltage is applied betweenthe erosion electrode and nozzle body 300 which are separated by anelectrically isolating fluid and this voltage causes an electricalbreakdown through the fluid. In the fluid, the breakdown produces adischarge path through which an electrical current flows and in whichthe temperature and pressure both remain high. There is a melting chargeat erosion electrode 701 and nozzle body 300 and material is vaporized.The material thus removed is carried off by the fluid. The material ofthe erosion electrode consists preferably of tungsten, silver, hardmetal or graphite. Water is preferably used as the fluid.

Pressure resistance can also be advantageously increased if the edges inthe area of the lowest wall thickness d are also chamfered, e.g., viaelectrochemical rounding.

What is claimed is:
 1. Fuel injection valve with a nozzle body having aguide area at a face end of the nozzle body, the guide area including acentral guide hole, a pressure chamber area which connects to the guidearea and has a pressure chamber into which the guide hole opens, asupply channel of the guide area which is located to a side of the guidehole and which opens into the pressure chamber, a nozzle holder body,and a hollow cylindrical intermediate piece disposed between the nozzlebody and the nozzle holder body, characterized in that the entire supplychannel of the guide area is curved, the guide area is stepped by afirst step cut into an upper body section with a face and into a lowerbody section with a locating face, the guide hole has a hole opening onthe face, the supply channel of the guide area has a supply opening onthe locating face of the lower body section, the lower body section iscloser than the upper body section to the pressure chamber area. theupper body section has a smaller diameter than the lower body section,the hollow cylindrical intermediate piece has a central plunger hole forguiding a plunger and a supply channel of the intermediate piece to theside of the plunger hole, the supply channel of the guide area is curvedin an approximately circular manner, and the intermediate piece at itsside facing the plunger hole is divided by a step cut into a hollowcylindrical supply area and into a hollow cylindrical plunger area. 2.Fuel injection valve according to claim 1, characterized in that thecurve in the supply channel of the guide area has a first radius at itscenterline of between 30 mm and 50 mm.
 3. Fuel injection valve accordingto claim 1, characterized in that an angle between the supply channel ofthe guide area at its opening into the pressure chamber and the guidehole is between 30° and 40°.
 4. Fuel injection valve according to claim1, characterized in that the curve in the supply channel of the guidearea has a second radius at its centerline of between 5 mm and 10 mm. 5.Fuel injection valve according to claim 4, characterized in that anangle between the supply channel of the guide area at its opening to thepressure chamber and the guide hole is between 40° and 70°.
 6. Fuelinjection valve according to claim 1, characterized in that the plungerarea is closer than the supply area to the nozzle holder body, theplunger area has a smaller inside diameter than the supply area, and thesupply channel of the intermediate piece is located in a casing of thesupply area and the plunger area.